BIOL 1104 Lecture Notes - Lecture 22: Echinoderm, Deuterostome, Chordate
Document Summary
Other difference between protostomes and deuterostomes: type of cleavage. Indeterminate cleavage : each cell in the early stages of cleavage retains the capacity to develop into a complete embryo. All protostomes and some deuterostomes are invertebrates : they lack a. Invertebrates make up 95% of known animal species. Vertebrates are a clade within the chordates . The deuterostomes include 3 phyla: the hemichodates, the chordates, and the echinoderms relative to the chordates. Echinoderms (sea stars, sea urchins, sea cucumbers) are the closest living. Most adult echinoderms have radial symmetry with multiples of five. All chordates share a set of derived characters. But some of these traits only appear during embryonic development in some species. Vertebrates are part of the phylum: chordata (the chordates) In some chordates, some the traits are visible only at the embryonic stage. Jaws appear to have evolved from pharyngeal arches. The first chordates were jawless little fishy things.